The packaging industry makes and uses many sheet structures in the making of heat sealed packages. Such packages find use in a multiplicity of applications. Of particular interest to the invention herein are those applications where the finished package may be subjected to relatively abusive physical shocks, as by being dropped, bumped, or the like. In cases where the package contains fluid components, the shock may be transferred to all parts of the package by the contained fluid. The transferred shock is effective to cause failure of the package at its weakest point when the severity of shock is sufficiently great.
Heat sealed packages tend to fail at or close to a heat seal. Typical failures occur by partial peeling of the facing sealant layers from each other in the seal area. Where the shock is severe enough, the package may have a catastrophic failure wherein the package may be penetrated to the outside.
Such failure of the package, whether by partial peeling or by catastrophic failure, compromises the containment and protective functions of the package, and is thus not acceptable. It is desirable to find material compositions which may be used in packaging sheet structures which compositions enhance the capability of the sheet structure, and particularly the sealant layer, to withstand increased amounts of shock-type abuse.
In certain packaging applications, the packages are subjected to heat treatment at elevated temperatures of up to about 250.degree. F. as part of the packaging process. Such heat treatments are common in certain packaging of medical supplies and shelf stable foods.
Some polymers, such as polypropylene, which are otherwise excellent for use with high temperature applications, tend to become more brittle after being subjected to such heat treatments. Increasing brittleness leads to less ability to resist shock type abuse. While the use of such materials is desirable for their ability to withstand heat treatment without failure of the package during the heat treatment, the resulting brittleness is an undesirable feature as affects its ability to withstand the shocks of, for example, shipping and handling.
It is an objective of this invention to provide novel material blend compositions.
It is further object of this invention to provide single layer films and multiple layer films and sheet structures, incorporating therein the novel compositions, for use in making packages, and particularly heat sealed packages.
Yet another object is to provide heat sealed packages capable of withstanding increased amounts of physical shock type abuse, especially after the closed and sealed package has been subjected to elevated temperatures of up to about 250.degree. F.